THE THEORY BEHIND
THE FORCE VECTOR
Any time you enter a corner, land
sideways from a jump or swap ends in
the whoops, you are trying to convert
inertia (force stored by a mass moving
along a straight line) into lateral accel-
eration (the G-forces that we feel in a
turn). This change in direction creates
a “force vector”—a line of equilibrium
between the two paths.
To arrive at this imaginary “force
vector” angle, you divide how many
degrees you deviate from a straight
line in half. The resulting angle happens to be exactly how much you need
to lean a motocross bike to counter
the cornering forces. For instance, a
90-degree change in direction requires
a 45-degree lean angle.
Any lean angle that exceeds the
force vector reduces the available
traction and causes the bike to want
to low-side (slide out). Any lean angle
less than the force vector moves the
motorcycle’s center of gravity to the
outside of the corner and into the
dreaded high-side zone. What typically
causes a high-side? (1) Tightening the
radius of the corner at the last second.
( 2) Shifting your weight too far to the
outside of the optimum lean angle. ( 3)
Entering a turn with too much speed
to be countered by lean angle.
Sir Isaac Newton said that bodies
in motion must remain in motion
unless acted upon by an outside force.
Conversely, no lean means no turn.
If you have failed to develop enough
cornering force, the mass of you and